This small book was the first attempt of this writer at writing a book. The year was 1985 and facilities at the Shariah Academy of the International Islamic University were limited. The manuscript was prepared on a typewriter and it was this typewritten text that was published by the Academy. The result was not very pleasing, as there were a large number of typographical and other errors, besides a misalignment of the references. This was the output despite several attempts at correcting and revising the text.